Didymium vernum Kuhnt, K. Baumann & Nowotny

Fructification
Sporocarps scattered, individual or in small groups of 2-10, sessile, pulvinate with circular or somewhat irregular circumscription, with constricted base. Up to ca. 1 mm Ø.

Hypothallus
Hypothallus inconspicuos, membranous and often with ochraceous lime scales as peridium.

Peridium
Peridium brownish grey in RL, with scattered, ocraceous stellate lime scales. In TL thin, membranous, hyline, with irregular, bright yellow patches.

Columella
None.

Capillitium
Capillitium of thin, almost hyaline to pale brownish threads, ± parallel, wavy and with many transverse connections, hardly expanded at nodes.

Spores
Spores globos or slightly ellipsoid, dark brown in RL, medium greyish brown in TL, with ± regularly distributed, medium sized short spines, 9-9.74-10.5 µm Ø (n=25).

Plasmodium
Not seen.

Ecology
On underside of leaf of Petasites hybridus.

Distribution in Denmark
Only one location is known at present: Copenhagen, Fælledparken.

Global distribution
Being described only recently the global distribution is not known, but it seems likely that Didymium vernum is widespread in Europe, following the host, to which it apparently is restricted.

Kuhnt, Baumann and Nowotny mentions finds from Germany and France. Further it is known from The Netherlands (Hooff, pers. com.) and Denmark. Additional finds from Germany have been reported in the internet forum Pilzforum.eu

Discussion
Didymium vernum Kuhnt, K. Baumann & Nowotny was desribed in a paper by Kuhnt, Andreas; Baumann, Karlheinz & Wolfgang Nowotny in the spring of 2014 along with the revitalization of Didymium tussilaginis (Berk. & Broome) Massee.
I am grateful to Hans van Hooff for making me aware of this paper, which inspired me to search for the two species in Denmark - with success.

Despite the fact that only one locality in Denmark for Didymium vernum is known at present, there is reason to believe that it is widespread, although not as common as Didymium tussilaginis, which occurs in the same habitat.

Description
The description and discussion is based on one Danish collection: hfg 2427.

 


Abbreviations: TL : transmitted light; RL : reflected light; Ø : diameter; TBU : Danish Botanical Topographical District.

Colour-codes refer to: Kornerup, A. & J. H. Wanscher 1974: Farver i farver. 5th reprint. Politikens Forlag, Copenhagen.

When not otherwise indicated spore measurements are given as: min-mean-max or (extreme-)min-mean-max(-extreme). Spore measurements are exclusive of ornamentation.

Line drawings are free hand sketches.

Didymium vernum Kuhnt, K. Baumann & Nowotny:
Didymium vernum Kuhnt, K. Baumann et Nowotny - Sporocarps (hfg2427)
Sporocarps
Didymium vernum Kuhnt, K. Baumann et Nowotny - Spores and capillitium (hfg2427)
Spores and capillitium
Didymium vernum Kuhnt, K. Baumann et Nowotny - Spores (hfg2427)
Spores